Injection molded synthetic wheel

ABSTRACT

A wheel of synthetic material for bicycles and the like. The wheel includes a rim, a plurality of spokes, and a hub, and is made in one piece by means of injection molding at the hub. Between each two adjacent spokes, the rim has a wall element which extends in the circumferential direction of the rim, extends from the connection location of each spoke on the rim to the middle of the rim portion between two spokes, and is rheologically designed as a preliminary flow cross-sectional area such that preliminary flows of the synthetic material enter the wall element from both spokes and flow more quickly from the two spoke connection locations to the middle of the rim portion than the two circumferential flows of synthetic material which advance in the remaining rim walls. This prohibits the two circumferential flows in the remaining rim walls from meeting at the middle of the rim portion and forming a cold flow seam which would considerably reduce the strength of the rim at this central rim portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wheel of synthetic material forbicycles or the like, for example for other single-track vehicles. Thewheel has a rim, which is approximately U-shaped in cross section, for atubed or tubeless tire; the wheel also has spokes which are unitarilymolded onto the rim via injection molding which originates from thewheel hub.

2. Description of the Prior Art

In general, during manufacture of a wheel of synthetic material byinjection molding in a mold, the wheel must, due to its geometricalshape, and in order to achieve optimum material properties, be centrallyinjection molded at the wheel hub, from where the synthetic materialflows in the mold to the wheel rim. However, when a wheel comprising arim, spokes, and hub is being homogeneously manufactured completely outof synthetic material, drawbacks result at the rim after the syntheticmaterial has flowed through the spokes in the mold. These drawbacksresult from the formation of a flow seam approximately in the middle ofthe rim portion between each two adjacent spokes. This formation of flowseams, especially with the use of synthetic material which is reinforcedwith glass fibers, leads to a considerable reduction of the ruggedness,the impact strength, and the appearance of the rim at these middle rimportions. Attempts were made to circumvent these disadvantageous flowseam formations in the rim profile of a spoked wheel of syntheticmaterial by means of a multiple injection molding of the wheel at therim. However, wheels produced pursuant to this method, have a greattendency toward distortion due to the varying pressure and shrinkageconditions in the mold. Furthermore, the formation of flow seams occursin the vicinity of the hub of the wheel, as a result of which theproblems of cold flow seams at the synthetic material hub, whichreceives the wheel bearings and is subjected to great stresses, lead toa particularly critical reduction in strength.

An object of the present invention is to avoid the drawbacks ofheretofore known wheels of synthetic material, while still providing forinjection molding which originates at the wheel hub.

BRIEF DESCRIPTION OF THE DRAWING

This object, and other objects and advantages of the present invention,will appear more clearly from the following specification in conjunctionwith the accompanying drawing, in which:

FIG. 1 is a side view of a portion of one exemplary embodiment of theinventive wheel of synthetic material;

FIG. 2 is a view that shows a radial cross section through the wheeltaken along line 11--II in FIG. 1;

FIG. 3 is a view that shows a radial section taken along the lineIII--III in FIG. 1;

FIG. 4 is a view that shows a radial section taken along line IV--IV inFIG. 1;

FIG. 5 is a view that shows a radial section through another inventiveembodiment of a wheel of synthetic material; and

FIG. 6 is a view that shows a radial section through a further inventiveembodiment of a synthetic material wheel for a tubeless tire.

SUMMARY OF THE INVENTION

The inventive synthetic material wheel for avoiding the aforementionedflow problems and disadvantageous flowseam formations in the rim profileis characterized primarily in that the rim, between each two adjacentspokes, is provided with wall elements which extend in thecircumferential direction of the rim from the connection location ofeach spoke to the rim to the middle of the rim portion located betweentwo spokes; the wall elements are rheologically designed preliminaryflow cross-sectional areas such that the synthetic material in thesewall elements flow more quickly from the spoke connection locations tothe middle of the rim portion than in the remaining rim walls.

In so doing, the following is achieved. Without the inventive wallelements, the synthetic material which flows into the rim through one ofthe stokes is distributed at the spoke connection location over thecross-sectional area of the rim and flows into the rim walls with afront which advances relatively uniformly in the circumferentialdirection of the rim and to the middle of the rim portion between twoadjacent spokes while at the same time cooling off; in this middleportion of the rim, the synthetic material meets a circumferential flowwhich arrives in the same manner through the rim walls from an adjacentspoke while forming a flow seam between two circumferential flows at areduced ruggedness and impact strength. In contrast, with the inventiverheologically acting wall elements, which are designed as preliminaryflow cross-sectional areas, there occurs in these wall elements a moreintensive and rapid preliminary flow of the synthetic material in thecircumferential direction of the rim due to the larger volume, relativeto the remaining rim walls, and due to the therefore slower cooling andsetting of the synthetic material from the outside toward the inside inthese wall elements. This more intensive and more rapid preliminary flowof the synthetic material in the circumferential direction of the rimleads the circumferential flow in the remaining rim walls and reachesthe middle of the rim portion between two adjacent spokes ahead of thiscircumferential flow. Accompanied by simultaneous pressure build up inthe preliminary flow cross-sectional areas, the preliminary flow meetsthe preliminary flow coming in a similar manner from the adjacent spokeat the middle of the rim portion, so that the two preliminary flows,before the circumferential flows in the remaining rim walls can meet atthe center of the rim portion, begin, as they are distributed over theentire periphery of the rim portion, to flow into the remaining rimwalls, which extend partially in the axial direction of the wheel, andpartially in the radial direction of the wheel. In this manner, thefilling of the rim portion over its circumferential length is madeuniform in place and time, and the disadvantageous formation of coldflow seams at the middle of the rim portion is avoided. Tests have shownthat a synthetic material wheel which is designed and manufactured withthe inventive rim wall elements has a considerably higher strength ofthe rim than does a wheel which is designed an manufactured withoutthese rim wall elements.

The inventive rim wall element, which is designed and operates as apreliminary flow cross-sectional area, for example, can comprise abead-like or rib-shaped widened cross-sectional area portion whichprojects from the base on the inner surface of the U-shaped rim. Thiswidened portion extends in the circumferential direction of the rim overthe connection locations of these spokes on the outer surface of the rimto the remaining rim walls. With this embodiment, the wall elementitself, of an additional rim wall element which extends in thecircumferential direction of the rim, pursuant to a further feature ofthe present invention, at the same time can be designed in such a waythat between these wall elements and the two sides of the rim twoannular grooves are formed for receiving the sides of a tire;furthermore, the lateral distance of the wall element from the two rimsides, and the radial height of the wall element, are such that when thetire sides are placed in the annular grooves, they always, even in casea central offset exists between the rim and the tire, make contact withthe rim sides due to the wall element. This inventive embodiment of therim has the further great advantage that the wheel is particularlysuitable for use with a tubeless tire, because after mounting the tireengages the rim sides all around in a satisfactory and air impermeablemanner, so that it can be easily inflated with a hard pump, for examplea conventional bicycle pump, and does not, after mounting, first have tobe spread apart and pressed outwardly by the rapid introduction of largequantities of air to such an extent that it begins to sealingly restagainst the sides of the rim.

Pursuant to a preferred embodiment of the present invention, the wallelement comprises a rim web or element which projects from the outersurface of the rim and has its ends connected to the spokes. Thatperipheral edge of the rim element which merges with the remaining rimwalls preferably has a cross-sectional width which becomes smaller fromthe middle of the rim portion toward the spokes.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawing in detail, the inventive wheel of syntheticmaterial comprises a rim 1, which has an approximately U-shaped crosssection, a plurality of spokes 2, which are unitarily molded with therim, and a non-illustrated wheel hub, starting from which the syntheticmaterial wheel is injection molded during manufacture in a mold. The rimprofile comprises as customary, relatively thin rim walls, two sides 3and a base 4, to which are connected the spokes 2 at connectionlocations 5. Each rim portion between two adjacent spokes 2 is providedwith a wall element which, starting from the connection location 5 of agiven one of the spokes 2, extends in the circumferential direction ofthe rim to the middle of the rim portion between two spokes, and which,relative to the flow cross-sectional area of the remaining rim walls 3and 4, rheologically has a larger volume preliminary flowcross-sectional area such that the synthetic material, which at thespoke connection locations 5 flows out of the spokes 2 into the rimprofile, flows more quickly in this wall element from the spokeconnection locations toward the middle of the rim portion than it doesin the remaining rim walls 3 and 4. In a preferred and rheologicallyadvantageous manner, this wall element is formed at the base 4 of therim profile, and, as illustrated in the embodiment of FIGS. 1 to 4,comprises a rim web or element 6 which projects from the surface of therim, and the ends of which are connected to the spokes. The element 6can have a radial cross-sectional height which is desirable for anadditional reinforcement of the rim. The cross section of the element 6,which is preferably wider than the remaining rim walls 3 and 4, isfurthermore of such a size that the element 6 forms a large-volume flowchannel for the synthetic material. In this flow channel, therefore, aslower cooling and setting of the synthetic material from the wall ofthe mold to the core of the cross-sectional area takes place than is thecase with the remaining rim walls 3 and 4. As a result, starting fromthe connection locations 5 of two adjacent spokes 2, there occurs in theelement 6 a rheological preliminary flow of the synthetic materialtowards the middle of the rim portion; this preliminary flow, uponflowing and/or after reaching the middle of the rim portion along theentire circumferential length thereof, starts flowing into the rim base4 and radially into the rim sides 3, before the two circumferentialflows of the synthetic material progressing from the spoke connectionlocations 5 into the rim walls 3 and 4 reaches the middle of the rimportion between two adjacent spokes 2. This prevents the cold flow seamformation of the synthetic material at the middle of the rim portion. Inorder to promote the preliminary flow of synthetic material in theelement 6 toward the middle of the rim portion, the element preferablycan be designed in such a way that at its peripheral edge, which mergesinto the rim walls 3 and 4, it has a cross-sectional width 7 whichbecomes narrower proceeding from the middle of the rim portion towardthe spokes, i.e. the spoke connection locations 5, as illustrated inFIGS. 2 to 4. As a result, in the vicinity of the spokes the exit ofsynthetic material from the element 6 into the remaining rim walls 3 and4 is restricted and impeded, and a still more distinct rheologicalpreliminary flow in the element 6 forward the middle of the rim portionis produced.

In addition to, or in place of, the rim elements 6 on the outer surfaceof the rim, the rim, pursuant to a further specific embodiment of thepresent invention as illustrated in FIG. 5, also can be provided with arheological preliminary flow cross-sectional area in the form of awidened cross-sectional area portion 8 which projects on the innersurface of the rim from the base 4 in the manner of a bead or rib. Thelarge volume widened cross-sectional area portion 8 extends annularly inthe circumferential direction of the rim over all of the spokeconnection locations 5 and laterally merges into the base 4 viacross-sectional areas 9 which act in a restraining manner. The syntheticmaterial which enters the rim profile at a given spoke connectionlocation 5 is divided into a peripheral flow in the rim walls 3 and 4,and into a preliminary flow in the widened cross-sectional area portion8, from which part of the synthetic material which is distributed overthe periphery of the rim flows axially and radially through thecross-sectional areas 9 into the rim walls 3 and 4, although syntheticmaterial predominately flows preliminarily from two adjacent spokestoward the middle of the rim portion and after meeting at the middle ofthe rim portion flows into the rim walls 3 and 4 counter to theperipheral flows, in order in this way to prevent the development of acold flow seam between the two peripheral flows at the middle of the rimportion.

In the embodiment illustrated in FIG. 6, a wall section 10 is providedwhich projects from the base 4 on the inner surface of the rim. The wallsection 10 can have such an effective flow cross-sectional area formaterial flow in the peripheral direction of the rim that, similar tothe widened cross-sectional area portion 8 in the embodiment of FIG. 5,it acts as a large-volume rheological preliminary flow channel.Alternatively, the wall section 10 can also comprise a material-savingrib arrangement which complements the rheological preliminary floweffect of a rim element 6 disposed on the outer surface of the rim in amanner similar to that of the embodiment of FIGS. 1 to 4. In particular,the wall section 10 of the embodiment of FIG. 6 is designed in such away that between the section 10 and the two sides 3 of the rim twoannular grooves are formed for receiving the sides 11 of a tire. Thespace between a given wall section 10 and the adjacent side 3 of therim, in other words the axial opening of the two annular grooves, issuch that the two tire sides 11, after being inserted into these annulargrooves, are in contact with both the wall section 10 and the rim side3. Furthermore, the radial height of the wall sections 10 is such thatboth of the tire sides 11 will also extend into the annular grooves, andwill contact the rim sides 3 and the wall sections 10, if the tire ismounted in such a way that a central offset between the rim and the tireresults, which can occur due to the difference between the innerdiameter of the tire sides and the diameter of the rim base, which, forexample, is customary with bicycle tires. Consequently, the embodimentof FIG. 6 makes it possible to also be able to use on the wheel rim atubeless tire which already during mounting is pressed by the wallsection 10 against the side 3 of the rim in such a way that air which ispumped in does not escape or at least the escape of such air is limitedto such an extent that the tire can be pumped up and inflated with anordinary hand pump. A rim designed with wall sections 10 as in the abovedescribed embodiment of FIG. 6 is suitable for use with tubed tireswithout the tube or with special tubeless tires, and is likewiseadvantageous for other wheels the rims of which are connected with thewheel hub, for instance by means other than spokes, or the rim of whichis not unitarily produced with the spokes from synthetic material and issealed in an air tight manner at the spoke connection locations in anysuitable way.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawing, but alsoencompasses any modifications within the scope of the appended claim.

What we claim is:
 1. A wheel of synthetic material, comprising a hub andspokes and a rim,said rim including main rim walls having apredetermined rim cross section and being unitary with said spokes atspoke connection locations on said rim, said hub being unitary with saidspokes and being the injection-molding center part of the wheel, theimprovement therewith which comprises: said rim being provide with aplurality of circumferentially extending additional rim wall elements ofsynthetic material between all of said spokes, each of said wallelements leading from said spoke connection location of a given spoke tothe middle of a rim portion located between two adjacent spokes and eachof said wall elements being designed, in comparison with said main rimwalls with respect to the rheological cross-sectional area thereof, withan advance-flow cross-sectional area, the synthetic material in each ofsaid wall elements at the middle of said rim portion, where two of saidwall elements join one another, and the synthetic material in said mainrim walls of said rim portion between said two adjacent spoke connectionlocations being free from cold flow seams, in which each of said wallelements is a rim element connected to said spokes and which projectsradially inwardly from a surface of said rim and has two ends, one ofwhich merges with said connection location of a given spoke, and theother of which merges in the middle of a rim portion with an end ofanother rim element extending from an adjacent spoke, in which each ofsaid rim elements has a radially outwardly disposed circumferential edgewhich merges with said remaining rim walls, and which has a varyingcross-sectional width which steadily decreases in the direction from themiddle of a rim portion toward a spoke.